What characteristic of the modern door lock means its success is often unnoticed in daily life?

Answer

Its invisibility in successful operation

The genius of a device like the modern door lock, according to the analysis of its impact, lies in its invisibility when operating correctly. The success of Martin's invention is measured in the millions of daily interactions—the simple, unnoticed turning of a key or latching of a door—which demonstrates its pervasive utility. People tend to only notice the function of a lock when it fails or when they are denied access to the space it is supposed to secure. This ubiquity is precisely why inventors who solve everyday problems, even subtly, deserve specific attention.

What characteristic of the modern door lock means its success is often unnoticed in daily life?
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